Description: In this article, the authors study a set of cooperatively interacting units at criticality, and prove with analytical and numerical arguments that they generate the same renewal non-Poisson intermittency as that produced by blinking quantum dots.

Description: In this paper, the authors show using scanning tunneling microscopy, spectroscopy, and ab initio calculations that several intercalation structures exist for Na in epitaxial graphene on SiC(0001). Intercalation takes place at room temperature and Na electron-dopes the graphene. It intercalates in-between single-layer graphene and the carbon-rich interfacial layer. It also penetrates beneath the interfacial layer and decouples it to form a second graphene layer. This decoupling is accelerated by annealing and is verified by direct Na deposition onto the interface layer. The authors' observations show that intercalation in graphene is fundamentally different than in graphite and is a versatile means of electronic control.

Description: This article demonstrates that the observed variability cannot be explained by X-ray Binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole.